Curtiss YP-37 / Model 75I

Primary-Source Operation, Flight & Allison V-1710 Engine Documentation Archive

The Curtiss YP-37 — factory designation Model 75I — stands as one of the most technically ambitious and operationally troubled experimental fighters of the pre-war era. Conceived as a direct adaptation of the proven P-36 Hawk airframe to the liquid-cooled, turbosupercharged Allison V-1710 inline engine, the YP-37 programme pushed the boundaries of 1930s propulsion engineering while exposing the severe limitations of early turbosupercharger technology. This archive brings together the surviving original military and manufacturer documentation for the YP-37 platform in a single structured collection.

Archive Manifest

• Handbook of Operation and Flight Instructions — Model YP-37 Pursuit Airplane
  Technical Order No. 01-25CC-1
  Curtiss Aeroplane Division, Curtiss-Wright Corp., Buffalo, N.Y.
  Contract W535 AC-10535 — Specification Type Model 6724
  Note: Replaces T.O. No. 01-25CC-1 dated July 25, 1938
  Published by Authority of the Chief of the Air Corps, Materiel Division, Field Service Section, Wright Field, Dayton, Ohio
  Dated: August 20, 1940
• Handbook of Operation and Maintenance — Allison V-1710 "E"-Type Engines
  Third Edition
  Allison Division of General Motors Corporation, Indianapolis, Indiana, U.S.A.

Aerodynamic Design & Layout

• Fuselage Extension: Forward fuselage extended by 22 inches (further lengthened on the 13 service-test YP-37 variants) to house the long V-12 engine block — substantially reducing frontal area drag versus the radial P-36
• Radiator Installation: Two Prestone cooling radiators and an intercooler integrated directly into the fuselage behind the engine, fed by cooling scoops on either side of the nose
• Wing Profile: Retained the standard low-wing, all-metal monoplane structure of the P-36 Hawk — NACA 2215 airfoil at the root tapering to NACA 2209 at the tip

Engine Technical Notes — Allison V-1710-21

• Powerplant: Liquid-cooled Allison V-1710-21 inline engine — 1,150 hp
• Turbosupercharger: Exhaust-driven General Electric B-2 turbosupercharger, mounted internally behind the engine block; its bulk forced reallocation of fuel tanks and electronics over the centre of gravity
• Thermal Limitations: Chronic overheating of turbosupercharger bearings and exhaust manifolds, liquid leaks, and mid-flight engine fires severely limited operational testing and ultimately ended the programme

Handling & Stability Characteristics

• Cockpit Relocation: Chief Designer Donovan Berlin moved the enclosed cockpit far aft — directly against the vertical tail surfaces — to counterbalance the heavy V-12 engine and cooling system
• Visibility: Flight test notes document virtually nonexistent downward, forward, and taxiing visibility; pilots could not see the runway during approaches or takeoffs
• CG & Stability: Auxiliary fuel tank relocated over the wing cured tail-heavy behaviour; longitudinal stability adequate in clean flight, but poor lateral tracking at low speeds due to the long nose blanketing control surfaces at high angles of attack

Performance Data — YP-37 Service-Test Standard

• Maximum Speed: 340 mph (547 km/h) at 20,000 ft
• Cruising Speed: 304 mph (489 km/h)
• Service Ceiling: 35,000 ft
• Rate of Climb: 3,400 ft/min — reaching 20,000 ft in 7.1 minutes
• Operational Range: 485 miles (780 km)
• Gross Weight: 6,350 lbs (2,880 kg)
• Armament: One .30-cal and one .50-cal machine gun in the nose

Engineering Bulletins & Programme Outcome

• Programme Cancellation: Despite impressive high-altitude speed profiles, constant mechanical breakdowns of the GE turbosupercharger proved insurmountable for USAAC operational requirements
• Legacy — Birth of the XP-40: In 1939, Curtiss engineers installed a mechanically supercharged Allison V-1710-19 in the tenth production P-36 airframe (Model 75P), returning the cockpit to a conventional forward position. The resulting XP-40 prototype won the 1939 Pursuit Competition and evolved into the iconic P-40 Warhawk. All 13 YP-37s were retired and transferred to ground technical training schools.

This is an archival, static-copy edition fixed at its original publication date. Intended for historical reference, flight simulation, museum restoration, and educational use only. Not approved for active airworthiness maintenance under FAA 14 CFR § 43.13, EASA Part-M, or equivalent international regulations. Operators of active aircraft must use current, revision-controlled publications from the Type Certificate holder or an authorized distributor.

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